Optical module and reflective encoder

Abstract

To provide an optical module and a reflective encoder capable of achieving miniaturization, suppressing an increase in noise, and achieving stable connection.SOLUTION: In the photodetecting device 12 of the optical module 3, a first conductivity type first semiconductive region 23 is formed on the side of the first surface 21a of the semiconductive substrate 21, and a second conductivity type second semiconductive region 24 is formed on the side of the second surface 21b. A through-hole 22 is formed in the substrate 21, and an inner surface 22a of the through-hole 22 includes a portion extending along a direction perpendicular to the first surface 21a. The second region 24 is electrically connected to the P1 of the supporting body 11 by the metallic layer 27. The metallic layer 27 is formed so as to extend from the second surface 21b and cover the inner surface 22a of the through hole 22. The metal layer 27 has a stacked portion 30 including an Au layer and an Al layer. The laminated portion 30 is formed so as to extend from the second surface 21b to the inner surface 22a of the through hole 22.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical module for a reflective encoder, and a reflective encoder. [Background technology]

[0002] Patent Document 1 describes an optical module for a reflective encoder in which a photodetector and a light-emitting element are arranged on a support (FIG. 4). In this optical module, a through-hole is formed in a semiconductor substrate that constitutes the photodetector, and a light-emitting element is arranged in the through-hole. A coating layer that reflects light from the light-emitting element is formed on the inner surface of the through-hole. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-193417 Summary of the Invention [Problem to be solved by the invention]

[0004] In the optical module described above, the through hole is tapered, making it easy to form a metal layer (coating layer) by, for example, vapor deposition or sputtering. Meanwhile, to reduce the size of the optical module, it is possible to form at least a portion of the inner surface of the through hole vertically. However, in this case, there is a risk that the metal layer will not be formed properly, which may reduce the light-blocking properties of the inner surface of the through hole and increase noise. Therefore, optical modules may be required to suppress increases in noise while achieving miniaturization. Furthermore, optical modules may be required to provide stable electrical connections between components.

[0005] Therefore, an object of the present invention is to provide an optical module and a reflective encoder that can be miniaturized, can suppress an increase in noise, and can achieve a stable connection. [Means for solving the problem]

[0006] The optical module of the present invention is [1] "an optical module for a reflective encoder, comprising: a support provided with electrode terminals; a photodetector element electrically connected to the electrode terminals; and a light-emitting element arranged on the support; the photodetector element has a semiconductor substrate having a first surface and a second surface opposite to the first surface, and is arranged on the support so that the second surface faces the support; at least one first semiconductor region of a first conductivity type that constitutes one of the anode and cathode of a photodiode is formed on the side of the first surface of the semiconductor substrate; at least one second semiconductor region of a second conductivity type that constitutes the other of the anode and cathode of the photodiode is formed on the side of the second surface of the semiconductor substrate; and a through-hole that penetrates from the first surface to the second surface of the semiconductor substrate is formed in the semiconductor substrate." an inner surface of the through hole includes a portion extending along a direction perpendicular to the first surface, and when viewed from the direction perpendicular to the first surface, the at least one first semiconductor region is located on both sides of the through hole in a predetermined direction; a metal layer is formed on the second surface of the semiconductor substrate, and the at least one second semiconductor region is electrically connected to the electrode terminal of the support by the metal layer, the metal layer is formed to extend from the second surface to cover the inner surface of the through hole, the metal layer has a laminated portion including an Au layer and an Al layer disposed between the Au layer and the semiconductor substrate, and the laminated portion is formed to extend from the second surface to reach the inner surface of the through hole; and the light-emitting element is arranged on the support to be located within the through hole.

[0007] In this optical module, the inner surface of the through hole formed in the semiconductor substrate includes a portion extending in a direction perpendicular to the first surface. This reduces the dead area in the semiconductor substrate, thereby enabling miniaturization of the optical module (in a direction parallel to the first surface). Furthermore, when viewed from a direction perpendicular to the first surface, the first semiconductor region constituting the photodiode is located on both sides of the through hole in a predetermined direction. This allows the photodiode to effectively detect light emitted from the light-emitting element in the through hole and reflected by the rotating plate. Furthermore, a metal layer is formed extending from the second surface of the semiconductor substrate to cover the inner surface of the through hole. This allows the metal layer to block light from the light-emitting element. As a result, this light is prevented from entering the semiconductor substrate from the inner surface of the through hole, traveling through the semiconductor substrate, and entering the photodiode, resulting in its detection as noise. Furthermore, the metal layer has a laminated portion including an Au layer and an Al layer disposed between the Au layer and the semiconductor substrate, and the laminated portion is formed extending from the second surface of the semiconductor substrate to the inner surface of the through hole. This allows the metal layer to be formed more satisfactorily on the inner surface of the through hole than when the metal layer does not include an Al layer, thereby suppressing an increase in noise. Furthermore, the metal layer is formed so as to extend from above the second surface of the semiconductor substrate and cover the inner surface of the through hole, and the second semiconductor region is electrically connected to the electrode terminal of the support by the metal layer. This allows the second semiconductor region of the photodetector to be stably electrically connected to the electrode terminal of the support. Therefore, this optical module can be miniaturized, suppress an increase in noise, and achieve a stable connection.

[0008] The optical module of the present invention may be [2] "the optical module according to [1], wherein the at least one first semiconductor region includes a pair of first semiconductor regions, the photodiode includes a first photodiode and a second photodiode, one of the pair of first semiconductor regions forms the first photodiode together with the at least one second semiconductor region, and the other of the pair of first semiconductor regions forms the second photodiode together with the at least one second semiconductor region." In this case, light emitted from the light-emitting element in the through hole and reflected by the rotating plate can be more effectively detected by the photodiode.

[0009] The optical module of the present invention may be [3] "an optical module according to [1] or [2], wherein the laminated portion further includes (1) a Ti layer and (2) a Pt layer or Ni layer between the Al layer and the Au layer, in this order from the Al layer side." In this case, the Ti layer has high adhesion to the Al layer and a high reducing effect, so that it is possible to suppress the occurrence of poor connection with the Au layer due to the surface of the Al layer being oxidized to form alumina. In addition, the Pt layer or Ni layer can function as a barrier layer that suppresses diffusion of Ti into the Au layer. As a result, the reliability of the metal layer can be improved.

[0010] The optical module of the present invention may be [4] "the optical module according to any one of [1] to [3], wherein the light-emitting element is electrically connected to an electrode terminal provided on the support via a wire, and the wire is located within the through-hole." In this case, it is possible to suppress the generation of noise due to stray light caused by the wire. In addition, it is possible to bring the light-receiving surface of the light-detecting element closer to the rotating plate, thereby improving detection accuracy.

[0011] The optical module of the present invention may be [5] "the optical module according to any one of [1] to [3], in which the light-emitting element is electrically connected to an electrode terminal provided on the light-detecting element via a wire." In this case, the wire connection between the light-emitting element and the electrode terminal can be facilitated. Furthermore, the diameter of the through-hole can be reduced, enabling further miniaturization of the optical module. Furthermore, the light-emitting surface of the light-emitting element and the light-receiving surface of the light-detecting element can be brought closer to the same height. As a result, even if the position of the optical module is slightly misaligned with respect to the light reflection pattern of a rotating plate provided in an encoder, distortion of the light pattern incident on the light-receiving surface due to this misalignment can be suppressed.

[0012] The optical module of the present invention may be [6] "the optical module according to any one of [1] to [5], wherein the entire metal layer is constituted by the laminated portion, and the Al layer is in contact with the at least one second semiconductor region." In this case, it is possible to form a thick metal layer with high coverage.

[0013] The optical module of the present invention may be [7] "the optical module according to any one of [1] to [6], wherein a third semiconductor region of the second conductivity type is formed on the side of the semiconductor substrate facing the first surface so as to surround the through hole when viewed from a direction perpendicular to the first surface, and the third semiconductor region is electrically connected to the at least one second semiconductor region by the metal layer." In this case, carriers generated by light incident on a dead area (a region other than the first semiconductor region) around the through hole on the first surface can be prevented from becoming noise. Furthermore, since the third semiconductor region is electrically connected to the second semiconductor region by the metal layer, it is possible to prevent the third semiconductor region from being in a floating state.

[0014] The optical module of the present invention may be [8] "the optical module according to any one of [1] to [7], wherein the entire inner surface of the through hole extends in a direction perpendicular to the first surface." In this case, the optical module can be further miniaturized.

[0015] The reflective encoder of the present invention is [9] "a reflective encoder comprising an optical module according to any one of [1] to [8] and a rotating plate having a light reflection pattern." For the reasons described above, this reflective encoder can be made smaller, can suppress an increase in noise, and can achieve stable connection. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide an optical module and a reflective encoder that can be miniaturized, can suppress an increase in noise, and can achieve a stable connection. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view of a reflective encoder according to an embodiment. [Figure 2] FIG. 2 is a plan view of a light detection element. [Figure 3] FIG. 2 is a cross-sectional view of a metal layer. [Figure 4] FIG. 10 is a diagram showing the observation results when the metal layer does not include an Al layer in the first example. [Figure 5] FIG. 10 is a diagram showing the observation results when the metal layer includes an Al layer in the first example. [Figure 6] FIG. 10 is a diagram showing the observation results when the metal layer does not include an Al layer in the second example. [Figure 7] FIG. 10 is a diagram showing the observation results when the metal layer includes an Al layer in the second example. [Figure 8] FIG. 10 is a cross-sectional view illustrating a first modified example. [Figure 9] 10(a), 10(b), and 10(c) are plan views for explaining a second modified example, a third modified example, and a fourth modified example, respectively. DETAILED DESCRIPTION OF THE INVENTION

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, the same or equivalent elements are designated by the same reference numerals, and redundant description will be omitted. [Reflective Encoder]

[0019] As shown in Fig. 1, the reflective encoder 1 includes a rotating plate 2 and an optical module 3. The reflective encoder 1 is, for example, an absolute rotary encoder, and is a device for detecting the absolute angle of a measurement object. The reflective encoder 1 may also be configured as an incremental type.

[0020] The rotating plate 2 is fixed to a rotating shaft (not shown) and rotates together with the rotating shaft. The rotating plate 2 is formed, for example, in the shape of a disk, and is attached to the rotating shaft at its center so as to be disposed perpendicular to the axis of the rotating shaft. A light reflection pattern 2a that reflects light emitted from the optical module 3 is formed on the rotating plate 2. The light reflection pattern 2a represents a predetermined pattern such as a gray code. The light reflection pattern 2a is made of, for example, a metal film.

[0021] The optical module 3 is an encoder optical module applied to the reflective encoder 1, and is fixed so as to face a part of the rotating plate 2. More specifically, the optical module 3 faces a part of the light reflection pattern 2a. The optical module 3 has a photodetector element 12 and a light-emitting element 13, which will be described later. The reflective encoder 1 further includes a processing unit (not shown) constituted by, for example, a signal processing circuit. The processing unit is electrically connected to the optical module 3, and encodes the photodetection result of the photodetector element 12 of the optical module 3 to output a Gray code representing the absolute value of the rotation angle of the rotation shaft.

[0022] In the reflective encoder 1, when the light reflection pattern 2a is positioned on the optical axis of light emitted from the light emitting element 13 of the optical module 3, the light is reflected by the light reflection pattern 2a, and the reflected light enters the photodetector element 12 of the optical module 3. On the other hand, when the light reflection pattern 2a is not positioned on the optical axis of the light emitted from the light emitting element 13, the light from the light emitting element 13 passes through the rotating plate 2 and does not enter the photodetector element 12.

[0023] 1, the optical module 3 includes a support 11, a photodetector element 12, and a light-emitting element 13. In the optical module 3, light is emitted from the light-emitting element 13 toward the rotating plate 2, and the light reflected by the light reflecting pattern 2a of the rotating plate 2 is detected by the photodetection region (photodiode 26 described later) of the photodetector element 12.

[0024] The support 11 is, for example, a wiring board formed in a rectangular plate shape from glass epoxy resin. The support 11 has a flat surface 11a, on which a wiring portion including a plurality of electrode terminals P1 and P2 is formed. The photodetector element 12 is electrically connected to the electrode terminal P1, and the light-emitting element 13 is electrically connected to the electrode terminal P2 via a wire WR.

[0025] The light detection element 12 includes a semiconductor substrate 21. The semiconductor substrate 21 is formed in a rectangular plate shape from a semiconductor material such as silicon. The semiconductor substrate 21 has a first surface 21a and a second surface 21b opposite to the first surface 21a. The first surface 21a and the second surface 21b are, for example, flat surfaces that are perpendicular to the thickness direction of the semiconductor substrate 21 and parallel to each other.

[0026] The first surface 21a is a device surface, and a device section (not shown) composed of a wiring layer, an insulating layer, etc. is formed on the first surface 21a of the semiconductor substrate 21. The second surface 21b is a placement surface, and the semiconductor substrate 21 is placed on the support 11 so that the second surface 21b faces the support 11. In this example, the semiconductor substrate 21 is fixed to the support 11 with the second surface 21b in contact with the surface 11a of the support 11. In the following description, the direction perpendicular to the first surface 21a is defined as the Z direction, one direction perpendicular to the Z direction is defined as the X direction, and the direction perpendicular to the Z direction and the X direction is defined as the Y direction. As shown in FIG. 2, in this example, the semiconductor substrate 21 is formed in a rectangular shape with long sides parallel to the X direction and short sides parallel to the Y direction.

[0027] A through hole 22 is formed in the center of the semiconductor substrate 21, penetrating from the first surface 21a to the second surface 21b. That is, the through hole 22 is open to the first surface 21a and the second surface 21b. The through hole 22 has, for example, a rectangular or circular cross section (a cross section perpendicular to the Z direction). In this example, the through hole 22 has a uniform square cross section in the Z direction. The entire surface of the inner surface 22a of the through hole 22 extends along the Z direction. That is, the inner surface 22a does not include a portion inclined with respect to the Z direction, and the through hole 22 is configured as a vertical hole extending perpendicular to the first surface 21a.

[0028] A p-type (first conductivity type) first semiconductor region 23 is formed on the first surface 21a side of the semiconductor substrate 21. In this example, the first semiconductor region 23 is formed in a part of the first surface 21a so as to be exposed at the first surface 21a. The first semiconductor region 23 includes a pair of first semiconductor regions 23a, 23b. As shown in FIG. 2, the pair of first semiconductor regions 23a, 23b are located on both sides of the through hole 22 in the X direction and face each other across the through hole 22 in the X direction. The first semiconductor regions 23a, 23b are formed to have the same shape, and in this example, are formed to have a rectangular shape in a plan view (when viewed from the Z direction). Note that the first semiconductor regions 23a, 23b may be formed to have different shapes.

[0029] An n-type (second conductivity type) second semiconductor region 24 is formed on the second surface 21b side of the semiconductor substrate 21. In this example, the second semiconductor region 24 is formed over the entire second surface 21b so as to be exposed at the second surface 21b. An n-type third semiconductor region 25 is formed on the first surface 21a side of the semiconductor substrate 21. In this example, the third semiconductor region 25 is formed in a part of the first surface 21a so as to be exposed at the first surface 21a. More specifically, as shown in FIG. 2, the third semiconductor region 25 extends along the edge of the through hole 22 so as to surround the through hole 22 when viewed from the Z direction. The third semiconductor region 25 is electrically connected to the second semiconductor region 24 by a metal layer 27, which will be described later.

[0030] The first semiconductor region 23 constitutes one of the anode and cathode of the photodiode 26, and the second semiconductor region 24 constitutes the other of the anode and cathode of the photodiode 26. The photodiode 26 is a portion that performs photoelectric conversion and constitutes a photodetection region of the photodetector element 12. In this example, the photodiode 26 includes a first photodiode 26a and a second photodiode 26b. The first photodiode 26a is constituted by the first semiconductor region 23a and a portion of the second semiconductor region 24 that faces the first semiconductor region 23a, and the second photodiode 26b is constituted by the first semiconductor region 23b and a portion of the second semiconductor region 24 that faces the first semiconductor region 23b.

[0031] A metal layer 27 is formed on the second surface 21b of the semiconductor substrate 21. The metal layer 27 is formed over the entire second surface 21b and extends from above the second surface 21b to cover the entire inner surface 22a of the through hole 22. In other words, the metal layer 27 is formed continuously (integrally) from the second surface 21b to the inner surface 22a of the through hole 22.

[0032] The metal layer 27 has a laminated portion 30 in which multiple layers are stacked. In this example, the entire metal layer 27 is composed of the laminated portion 30. As a result, the laminated portion 30 is formed so as to extend from the second surface 21b of the semiconductor substrate 21 to the inner surface 22a of the through hole 22. In this example, the laminated portion 30 is formed over the entire second surface 21b and extends from the second surface 21b to cover the entire inner surface 22a of the through hole 22. The metal layer 27 formed on the inner surface 22a electrically connects the third semiconductor region 25 on the first surface 21a side and the second semiconductor region 24 on the second surface 21b side.

[0033] 3, the laminated portion 30 has, from the semiconductor substrate 21 side, an Al (aluminum) layer 31, a Ti (titanium) layer 32, a Pt (platinum) layer 33, and an Au (gold) layer 34, in this order. That is, the Al layer 31 is disposed between the Au layer 34 and the semiconductor substrate 21, and the Ti layer 32 and Pt layer 33 are disposed between the Al layer 31 and the Au layer 34, in this order, from the Al layer 31 side. The Al layer 31, the Ti layer 32, the Pt layer 33, and the Au layer 34 are layers made only of Al, Ti, Pt, and Au, respectively.

[0034] The Al layer 31 is formed on the second surface 21b of the semiconductor substrate 21 and on the inner surface 22a of the through-hole 22 by, for example, DC (direct current) sputtering, and has a thickness of approximately 1000 nm. The Al layer 31 formed on the second surface 21b is in contact with and electrically connected to the second semiconductor region 24. The Ti layer 32, the Pt layer 33, and the Au layer 34 are formed on the Al layer 31 by EB (electron beam) evaporation. The outermost Au layer 34 functions as a reflective layer that reflects light emitted from the light-emitting element 13. The Ti layer 32 prevents the surface of the Al layer 31 from oxidizing to form alumina, and the Pt layer 33 functions as a barrier layer that prevents Ti contained in the Ti layer 32 from diffusing into the Au layer 34.

[0035] The photodetector element 12 is disposed on the surface 11a of the support 11 and is electrically connected to an electrode terminal P1 of the support 11. More specifically, the photodetector element 12 is electrically connected to the electrode terminal P1 at a metal layer 27 on the second surface 21b of the semiconductor substrate 21. At the connection point, the electrode terminal P1 is in contact with and electrically connected to the metal layer 27 (the Au layer 34 of the laminated portion 30), and is electrically connected to the second semiconductor region 24 (the first photodiode 26a and the second photodiode 26b) via the metal layer 27.

[0036] The light-emitting element 13 is disposed on the surface 11a of the support 11 so as to be located within the through-hole 22. In this example, the entire light-emitting element 13 is located within the through-hole 22. The light-emitting element 13 is electrically connected to the electrode terminal P2 via the wire WR. As shown in FIG. 2 , in this example, the entire wire WR is located within the through-hole 22. [Observation results]

[0037] 4 to 7, the observation results will be described for the cases where the metal layer 27 includes and does not include the Al layer 31. Figs. 4 and 5 show the observation results for the first example, and Figs. 6 and 7 show the observation results for the second example.

[0038] The observation target in the first example shown in Figures 4 and 5 is a metal layer 27 formed on the inner surface 22a of a through-hole 22 in a photodetector element 12, where the through-hole 22 is circular and 150 μm in diameter. Figure 4 shows the observation results when the metal layer 27 does not include an Al layer 31, and Figure 5 shows the observation results when the metal layer 27 includes an Al layer 31. In each figure, the "first surface side" indicates the observation results on the side of the first surface 21a, the "second surface side" indicates the observation results on the side of the second surface 21b, and the "middle" indicates the observation results in the middle portion between the first surface 21a and the second surface 21b. In each figure, the right column indicates the observation results on the side of the orientation flat, and the right column indicates the observation results on the side opposite the orientation flat. These points are also true for Figures 6 and 7.

[0039] 4 and 5 show that when the metal layer 27 includes the Al layer 31, the metal layer 27 is formed well (with a sufficient thickness) on the inner surface 22a of the through hole 22, compared to when the metal layer 27 does not include the Al layer 31. As one of the evaluation criteria, in the case of FIG. 4, the metal layer 27 is not formed to the extent that electrical conductivity is achieved throughout the entire metal layer 27, whereas in the case of FIG. 5, the metal layer 27 is formed to the extent that electrical conductivity is achieved throughout the entire metal layer 27. When the metal layer 27 is formed with a sufficient thickness as shown in FIG. 5, light from the light-emitting element 13 can be reliably blocked. As a result, it is possible to effectively prevent the light from entering the semiconductor substrate 21 from the inner surface 22a of the through hole 22, traveling through the semiconductor substrate 21, and entering the photodiode 26, resulting in detection of the light as noise. The metal layer 27 is formed thicker on the second surface 21b side than on the first surface 21a side because the sputtering of the Al layer 31 and the deposition of the Ti layer 32, the Pt layer 33, and the Au layer 34 are performed from the second surface 21b side (the lower side in the figure).

[0040] 6 and 7, the observation target in the second example is a metal layer 27 formed on the inner surface 22a of a through-hole 22 in a photodetector element 12 in which the through-hole 22 has a rectangular shape of 560 μm × 505 μm. Fig. 6 shows the observation result when the metal layer 27 does not include the Al layer 31, and Fig. 7 shows the observation result when the metal layer 27 includes the Al layer 31.

[0041] 6 and 7 show that when the metal layer 27 includes the Al layer 31, the metal layer 27 is formed well (with a sufficient thickness) on the inner surface 22a of the through hole 22, compared to when the metal layer 27 does not include the Al layer 31. As one of the evaluation criteria, in the case of FIG. 6, the metal layer 27 is not formed to the extent that electrical continuity is achieved throughout the metal layer 27, whereas in the case of FIG. 7, the metal layer 27 is formed to the extent that electrical continuity is achieved throughout the metal layer 27. When the metal layer 27 is formed with a sufficient thickness as shown in FIG. 7, light from the light-emitting element 13 can be reliably blocked, as in the case of FIG. 5. As a result, it is possible to effectively prevent the light from entering the semiconductor substrate 21 from the inner surface 22a of the through hole 22, traveling through the semiconductor substrate 21, and entering the photodiode 26, resulting in detection of the light as noise. [Action and effect]

[0042] In the optical module 3, the inner surface 22a of the through hole 22 formed in the semiconductor substrate 21 includes a portion extending along the Z direction (a direction perpendicular to the first surface 21a). This reduces the dead area in the semiconductor substrate 21, thereby enabling the optical module 3 to be miniaturized (in a direction parallel to the first surface 21a). That is, for example, if the inner surface 22a of the through hole 22 is configured as an inclined hole inclined with respect to the Z direction, a dead area may be generated in the semiconductor substrate 21 due to the formation of the through hole 22. However, in the optical module 3, the inner surface 22a includes a portion extending along the Z direction, thereby reducing the dead area. Furthermore, in a plan view (when viewed from a direction perpendicular to the first surface 21a), the pair of first semiconductor regions 23a, 23b constituting the photodiode 26 are located on both sides of the through hole 22 in the X direction (a predetermined direction). This allows the photodiode 26 to effectively detect light emitted from the light-emitting element 13 in the through hole 22 and reflected by the rotating plate 2. Furthermore, a metal layer 27 is formed extending from above the second surface 21b of the semiconductor substrate 21 to cover the inner surface 22a of the through hole 22. This allows the metal layer 27 to block light from the light emitting element 13. As a result, this light is prevented from entering the semiconductor substrate 21 from the inner surface 22a of the through hole 22, traveling through the semiconductor substrate 21, and being incident on the photodiode 26, where it is detected as noise. Furthermore, the metal layer 27 has a stacked portion 30 including an Au layer 34 and an Al layer 31 disposed between the Au layer 34 and the semiconductor substrate 21, and the stacked portion 30 is formed extending from above the second surface 21b of the semiconductor substrate 21 to reach the inner surface 22a of the through hole 22. This allows the metal layer 27 to be formed more satisfactorily on the inner surface 22a of the through hole 22 than when the metal layer 27 does not include the Al layer 31, thereby preventing an increase in noise. Furthermore, a metal layer 27 is formed so as to extend from above the second surface 21b of the semiconductor substrate 21 and cover the inner surface 22a of the through-hole 22, and the second semiconductor region 24 is electrically connected to the electrode terminal P1 of the support 11 by the metal layer 27. This allows the second semiconductor region 24 of the photodetector element 12 to be electrically connected to the electrode terminal P1 of the support 11 in a stable manner.Therefore, the optical module 3 can be made smaller, can suppress an increase in noise, and can achieve a stable connection.

[0043] The first semiconductor region 23a, together with the second semiconductor region 24, constitutes a first photodiode 26a, and the first semiconductor region 23b, together with the second semiconductor region 24, constitutes a second photodiode 26b. This allows the photodiode 26 to more effectively detect light emitted from the light-emitting element 13 in the through-hole 22 and reflected by the rotating plate 2.

[0044] The laminated portion 30 includes a Ti layer 32 and a Pt layer 33, in this order from the Al layer 31 side, between the Au layer 34 and the Al layer 31. As a result, the Ti layer 32 has high adhesion to the Al layer 31 and a high reducing action, which can prevent the surface of the Al layer 31 from oxidizing to form alumina, thereby preventing poor connection with the Au layer 34. In addition, the Pt layer 33 can function as a barrier layer that prevents Ti from diffusing into the Au layer 34. As a result, the reliability of the metal layer 27 can be improved.

[0045] The light-emitting element 13 is electrically connected to an electrode terminal P2 provided on the support 11 via a wire WR, and the wire WR is positioned inside the through-hole 22. This makes it possible to suppress the generation of noise due to stray light caused by the wire WR. In addition, the light-receiving surface of the light-detecting element 12 can be brought closer to the rotating plate 2, thereby improving detection accuracy.

[0046] The entire metal layer 27 is made up of the laminated portion 30, and the Al layer 31 is in contact with the second semiconductor region 24. This makes it possible to easily form the metal layer 27.

[0047] An n-type third semiconductor region 25 is formed on the first surface 21a side of the semiconductor substrate 21 so as to surround the through-hole 22 in a plan view, and the third semiconductor region 25 is electrically connected to the second semiconductor region 24 by a metal layer 27. This makes it possible to prevent carriers generated by light incident on a dead area (a region other than the first semiconductor region 23) around the through-hole 22 on the first surface 21a from becoming noise. Furthermore, because the third semiconductor region 25 is electrically connected to the second semiconductor region 24 by the metal layer 27, it is possible to prevent the third semiconductor region 25 from being in a floating state.

[0048] The entire inner surface 22a of the through-hole 22 extends along the Z direction, which allows the optical module 3 to be further miniaturized. [Variations]

[0049] In the first modified example shown in FIG. 8 , the light-emitting element 13 is electrically connected to an electrode terminal P3 provided on the photodetector element 12 via a wire WR. In this example, a portion of the wire WR is disposed outside the through-hole 22 (i.e., protrudes outward). This first modified example, like the above embodiment, also enables miniaturization, suppresses noise increases, and achieves stable connection. It also facilitates wire connection between the light-emitting element 13 and the electrode terminal P3. It also enables the diameter of the through-hole 22 to be reduced, enabling further miniaturization of the optical module 3. Furthermore, it enables the light-emitting surface of the light-emitting element 13 and the light-receiving surface of the photodetector element 12 to be positioned nearly flush with each other. As a result, even if the position of the optical module 3 is slightly misaligned with respect to the light reflection pattern 2a of the rotating plate 2 of the reflective encoder 1, distortion of the light pattern incident on the light-receiving surface due to this misalignment can be suppressed.

[0050] The optical module 3 may be configured as shown in second, third, and fourth modified examples shown in FIGS. 9(a), 9(b), and 9(c). In the second modified example, the first semiconductor region 23 includes three first semiconductor regions 23a, 23b, and 23c. The first semiconductor region 23a is formed in a rectangular ring shape surrounding the through hole 22 in a plan view. The first semiconductor regions 23b and 23c are located on both sides of the through hole 22 in the X direction and face each other in the X direction with the through hole 22 and the first semiconductor region 23a sandwiched therebetween. In the second modified example, the first semiconductor regions 23b and 23c may not be formed, and only the first semiconductor region 23a may be formed. In this case, the first semiconductor region 23a is also located on both sides of the through hole 22 in the X direction (having portions located on both sides of the through hole 22 in the X direction).

[0051] In the third modified example, the through hole 22 is formed in an elliptical shape. In the fourth modified example, the through hole 22 is formed in a circular shape. Furthermore, the portions of the first semiconductor regions 23a, 23b on the through hole 22 side have a curved shape that follows the through hole 22. As with the above embodiment, these second to fourth modified examples also make it possible to achieve miniaturization, suppress an increase in noise, and achieve stable connection.

[0052] The present invention is not limited to the above-described embodiment and modifications. For example, the materials and shapes of the components are not limited to those described above, and various materials and shapes can be adopted.

[0053] For example, in the above embodiment, the entire inner surface 22a of the through hole 22 extends along the Z direction, but the inner surface 22a of the through hole 22 may include a portion inclined with respect to the Z direction. The shape of the through hole 22 does not have to be uniform in the Z direction. At least one first semiconductor region 23 needs to be provided, and one or three or more first semiconductor regions 23 may be provided. At least one second semiconductor region 24 needs to be provided, and one or three or more second semiconductor regions 24 may be provided. The photodiode 26 may be composed of one photodiode. The third semiconductor region 25 may be omitted. In the above embodiment or modified example, the p-type and n-type may be interchanged. That is, the first semiconductor region 23 may be n-type, and the second semiconductor region 24 and the third semiconductor region 25 may be p-type.

[0054] In the above embodiment or modified example, the Pt layer 33 may be replaced with a Ni layer made of Ni (nickel). At least one of the Ti layer 32 and the Pt layer 33 may be omitted. The entire metal layer 27 does not necessarily have to be composed of the laminated portion 30. Only a portion of the metal layer 27 may be composed of the laminated portion 30, and the remaining portion may be composed of a laminated portion including the Ti layer 32, the Pt layer 33, and the Au layer 34, without including the Al layer 31. In this case, the laminated portion 30 may be formed so as to extend from the second surface 21b of the semiconductor substrate 21 to the inner surface 22a of the through hole 22. For example, the laminated portion 30 may be formed only on a central portion of the second surface 21b rather than on the entire inner surface 22a of the through hole 22. The laminated portion 30 may be formed only on a portion of the inner surface 22a facing the second surface 21b rather than on the entire inner surface 22a of the through hole 22. The metal layer 27 does not necessarily have to be formed on the entire inner surface 22a of the through hole 22, but may be formed only on a portion of the inner surface 22a facing the second surface 21b. [Explanation of symbols]

[0055] 1...reflective encoder, 2...rotating plate, 3...optical module, 2a...light reflection pattern, 11...support, 12...photodetector, 13...light-emitting element, 21...semiconductor substrate, 21a...first surface, 21b...second surface, 22...through hole, 22a...inner surface, 23, 23a, 23b, 23c...first semiconductor region, 24...second semiconductor region, 25...third semiconductor region, 26...photodiode, 26a...first photodiode, 26b...second photodiode, 27...metal layer, 30...laminated portion, 31...Al layer, 32...Ti layer, 33...Pt layer, 34...Au layer, P1, P2, P3...electrode terminal, WR...wire.

Claims

1. An optical module for a reflective encoder, comprising: a support provided with electrode terminals; a photodetector element electrically connected to the electrode terminal; a light-emitting element disposed on the support, the light detection element has a semiconductor substrate having a first surface and a second surface opposite to the first surface, and is disposed on the support body such that the second surface faces the support body; at least one first semiconductor region of a first conductivity type that constitutes one of an anode and a cathode of a photodiode is formed on the first surface side of the semiconductor substrate; at least one second semiconductor region of a second conductivity type that constitutes the other of the anode and the cathode of the photodiode is formed on the second surface side of the semiconductor substrate; a through hole penetrating from the first surface to the second surface is formed in the semiconductor substrate; an inner surface of the through hole includes a portion extending along a direction perpendicular to the first surface; When viewed from a direction perpendicular to the first surface, the at least one first semiconductor region is located on both sides of the through hole in a predetermined direction, a metal layer is formed on the second surface of the semiconductor substrate, and the at least one second semiconductor region is electrically connected to the electrode terminal of the support by the metal layer; the metal layer is formed so as to extend from the second surface and cover the inner surface of the through hole, the metal layer has a stacked portion including an Au layer and an Al layer disposed between the Au layer and the semiconductor substrate; the laminated portion is formed to extend from the second surface to the inner surface of the through hole, The light emitting element is disposed on the support body so as to be positioned within the through hole.

2. the at least one first semiconductor region includes a pair of first semiconductor regions, and the photodiode includes a first photodiode and a second photodiode; 2. The optical module according to claim 1, wherein one of the pair of first semiconductor regions constitutes the first photodiode together with the at least one second semiconductor region, and the other of the pair of first semiconductor regions constitutes the second photodiode together with the at least one second semiconductor region.

3. 3. The optical module according to claim 1, wherein the laminated portion further includes, between the Al layer and the Au layer, (1) a Ti layer and (2) a Pt layer or a Ni layer, in this order from the Al layer side.

4. the light-emitting element is electrically connected to an electrode terminal provided on the support via a wire, The optical module according to claim 1 , wherein the wire is located within the through-hole.

5. 3. The optical module according to claim 1, wherein the light emitting element is electrically connected to an electrode terminal provided on the light detecting element via a wire.

6. 3. The optical module according to claim 1, wherein the entire metal layer is formed by the laminated portion, and the Al layer is in contact with the at least one second semiconductor region.

7. a third semiconductor region of the second conductivity type is formed on the first surface side of the semiconductor substrate so as to surround the through hole when viewed in a direction perpendicular to the first surface; 3. The optical module according to claim 1, wherein the third semiconductor region is electrically connected to the at least one second semiconductor region by the metal layer.

8. 3. The optical module according to claim 1, wherein the entire inner surface of the through hole extends in a direction perpendicular to the first surface.

9. an optical module according to claim 1 or 2; a rotating plate having a light reflecting pattern.

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